Correction of cluster defects in imagers

Abstract

A method and apparatus that allows for the correction of multiple defective pixels in an imager device. In one exemplary embodiment, the method includes the steps of selecting a correction kernel for a defective pixel, determining average and difference values for pixel pairs in the correction kernel, and substituting an average value from a pixel pair for the value of the defective pixel.

What is claimed as new and desired to be protected by Letters Patent of the United States is: 
     
       1. A method of correcting a defective pixel in an imaging circuit, said imaging circuit having an array comprising a plurality of pixels, said method comprising:
 identifying a pixel for correction; 
 selecting a first pair of pixels symmetrically located about the identified pixel and including a first pixel and a second pixel and a second pair of pixels symmetrically located about the identified pixel and, including a third pixel and a fourth pixel, said first pair of pixels and second pair of pixels being the nearest pixels of the same color as the identified pixel; and 
 determining if at least one of said first, second, third and fourth pixels are defective; 
 if said first, second, third, and fourth pixels are not defective: 
 determining an average pixel value and a difference pixel value for said first pair of pixels and said second pair of pixels; and 
 substituting said average pixel value of the one of said first pair of pixels and said second pair of pixels has the smallest difference pixel value for a pixel value of said identified pixel. 
 
     
     
       2. The method of  claim 1 , further comprising:
 at least one of the first, second, third and fourth pixels is a defective pixel, selecting third and fourth pairs of next nearest, same color pixels symmetrically located above the identified pixel for correction and 
 determining if there is at least one defective pixel in said third and fourth pairs of pixels, and if not:
 determining an average pixel value and a difference pixel value for said third pair of pixels and for said fourth pair of pixels; and 
 substituting said average pixel value of the one of said third pair of pixels and fourth pair of pixels which has the smallest difference pixel value for a pixel value of said identified pixel. 
 
 
     
     
       3. The method of  claim 1 , further comprising:
 if at least one of said first, second, third, and fourth pixels are defective, substituting a pixel value of a non-defective pixel for said pixel value of said pixel for correction. 
 
     
     
       4. The method of  claim 2 , wherein if there is at least one defective pixel in said third and fourth pairs of pixels, substituting a pixel value of a non-defective pairs of pixels, pixel for said pixel value of said identified pixel for correction. 
     
     
       5. The method of  claim 3 , wherein said non-defective pixel is a nearest non-defective pixel to said pixel for correction in said array that corresponds to a same color as said pixel for correction. 
     
     
       6. The method of  claim 4 , wherein said non-defective pixel is a nearest non-defective pixel to said identified pixel for correction in said array that corresponds to a same color as said identified pixel for correction. 
     
     
       7. A method of operating an imager, said imager having an array comprising a plurality of pixels, said method comprising:
 locating a defective pixel of a first color in said pixel array; 
 selecting a first plurality of closest neighboring pairs of pixels to the defective pixel in said pixel array, wherein each pair of pixels of said first plurality of pairs of pixels comprises a first pixel having said first color and a second pixel having said first color on an opposite side of said defective pixel from said first pixel; 
 determining if said first plurality of pairs of pixels includes any defective pixels; and 
 if said first plurality of pairs of pixels does not include any defective pixels: 
 determining an average pixel value for each pair of pixels in said first plurality of pairs of pixels; and 
 substituting an average pixel value of one of said pairs of pixels in said first plurality of pairs of pixels for a pixel value of said defective pixel. 
 
     
     
       8. The method of  claim 7 , wherein if said first plurality of pairs of pixels does not include any defective pixels, said method further comprises:
 determining a respective difference pixel value for each pair of pixels in said first plurality of pairs of pixels, wherein said respective difference pixel value for each pair of pixels comprises a difference between respective first and second pixels in said pair of pixels; 
 determining a lowest difference pixel value for said first plurality of pairs of pixels; and 
 substituting said average pixel value of said pair of pixels corresponding to said lowest difference pixel value for said pixel value of said defective pixel. 
 
     
     
       9. The method of  claim 7 , wherein if said first plurality of pairs of pixels including a defective pixel, said method further comprises:
 determining if a second plurality of pairs of next closest pixels to the defective pixel includes any defective pixels, wherein each pair of pixels of said second plurality of pairs of pixels comprises a first pixel having said first color and a second pixel having said first color on an opposite side of said known defective pixel from said first pixel; and 
 if said second plurality of pairs of pixels do not include any defective pixels: 
 determining an average pixel value for each pair of pixels in said second plurality of pairs of pixels; and 
 substituting an average pixel value of one of said pairs of pixels in said second plurality of pairs of pixels for said pixel value of said defective pixel. 
 
     
     
       10. The method of  claim 9 , wherein if second plurality of pairs of pixels does not include any defective pixels, said method further comprises:
 determining a respective difference pixel value for each pair of pixels in said second plurality of pairs of pixels, wherein said respective difference pixel value for each pair of pixels comprises a difference between respective first and second pixels in said pair of pixels; 
 determining a lowest difference pixel value for said second plurality of pairs of pixels; and 
 substituting said average pixel value of said pair of pixels corresponding to said lowest difference pixel value for said pixel value of said known defective pixel. 
 
     
     
       11. The method of  claim 9 , wherein if said second plurality of pairs of pixels includes at least one defective pixel, said method further comprises:
 identifying a nearest non-defective pixel to said known defective pixel having said first color; and 
 substituting a pixel value of said nearest non-defective pixel for said pixel value of said known defective pixel. 
 
     
     
       12. The method of  claim 7 , wherein said first plurality of pairs of pixels includes a first pair of pixels comprising:
 a first pixel having said first color located vertically above said defective pixel in said array; and 
 a second pixel having said first color located vertically below said defective pixel in said array. 
 
     
     
       13. The method of  claim 12 , wherein said first plurality of pairs of pixels further includes a second pair of pixels comprising:
 a third pixel having said first color located horizontally on a first side of said defective pixel in said array; and 
 a fourth pixel having said first color located horizontally on a second side of said defective pixel in said array, wherein said second side is an opposite side of said defective pixel than said first side. 
 
     
     
       14. The method of  claim 9 , wherein said second plurality of pairs of pixels includes a third pair of pixels comprising:
 a fifth pixel having said first color; and 
 a sixth pixel having said first color, wherein said fifth and sixth pixels are located diagonally symmetrical of said defective pixel in said array. 
 
     
     
       15. The method of  claim 14 , wherein said second plurality of pairs of pixels further includes a fourth pair of pixels comprising:
 a seventh pixel having said first color; and 
 an eighth pixel having said first color, wherein said seventh and eighth pixels are located diagonally symmetrically of said defective pixel in said array. 
 
     
     
       16. The method of  claim 7 , wherein said step of identifying a known defective pixel comprises identifying a pixel that is part of a cluster of defective pixels. 
     
     
       17. The method of  claim 7 , wherein said defective pixel is designated by a fuse. 
     
     
       18. The method of  claim 7 , wherein said step of identifying a defective pixel comprises locating said defective pixel using processing circuitry.